1. Field of the Invention
This invention relates to a paper shredder, particularly to a lubricating packet designed to be shredded by a paper shredders to provide lubrication to the cutting blades of the paper shredder.
2. Description of the Background
Paper shredders are common appliances that are used to render paper documents unreadable to prevent theft of private information such as financial information. It is relatively simple for someone to rifle through one's trash to discover account numbers and other data that can be used to perpetrate identity theft. Therefore, virtually all businesses and many private individuals shred all documents that contain private information. With a paper shredder papers are generally introduced through a slot or chute into a shredding mechanism. Most paper shredders employ a plurality of cutting blades spaced apart along counter rotating shafts as a shredding mechanism. A nip is formed between two such blade-bearing shafts, and sheets of paper inserted into the nip are sheared into fragments. Shredders can be generally classed into two types according to the shape of the fragments they produce. In the simplest type of shredder, the strip-cut shredder, the cutting blades on the rotating shafts cut the paper only in a longitudinal direction to form strips. While fairly difficult, it is possible to reassemble the strips to “regenerate” the original document and thus read the confidential information thereon. Most newer shredder are “cross cut” shredders that have blades that include more than one cutting edge per blade with these extra cutting edges disposed on the shaft to first cut the paper along a longitudinal direction into strips and to then cut the strips at an angle to the longitudinal direction to cut the strips into paper chips. These shredders produce a product not unlike confetti so that it is virtually impossible to reassemble the original document.
Unfortunately, the blades of the shredder—particularly the cross-cut shredder—become heated in use and bind dust and debris resulting from the shredding process. Furthermore, depending on air quality and humidity levels the blades may begin to corrode with time. These processes gradually reduce the efficiency of the shredders and may ultimately cause them to fail. One way of avoiding this problem is to apply a lubricant such as oil to the cutting mechanism. Unfortunately, it is relatively difficult to directly apply a lubricant to the rotating blades. Because of safety concerns the blades are usually sealed within the system and not readily accessible. Attempting to pour oil down the inlet slot or chute of an operating shredder is messy and may result in lubricant being sprayed back on the user—or worse.
The prior art solution to this problem is to enclose the lubricant in some sort of package. For example, patent applications to Zettler (DE 8702207) and to Holland (DE 3426979) contemplate enclosing a lubricant-bearing sheet, such as oil-soaked paper, in oil-resistant cover layers. Such a compound sheet or lubrication package can be easily and cleanly handled and inserted into an operating shredder to lubricate the shredder blades as they cut the compound sheet into fragments. These prior art references also contemplate sealing a liquid lubricant such as oil directly between oil-resistant cover layers and dispensing entirely with the lubricant-bearing sheet. In attempting to commercialize these prior art designs, it was discovered that an unanticipated problem was that as the lubrication package was drawn into the shredding mechanism, it was compressed resulting in the release of a puff of air containing oil droplets. These droplets can squirt out of the machine and/or deposit oil in regions of the shredder that should not receive oil. This problem is more severe in the liquid oil designs where the lubrication substrate is entirely dispensed with.
One solution to this problem is shown in U.S. Pat. No. 7,793,876 which discloses a plurality of vents arranged peripherally around the edges of the lubrication package. Because of the arrangement of peripheral seals, the lubricant is retained within the lubrication package until it is compressed during the shredding process. At that time, the vents relieve built up pressure and direct the compressed air and any oil droplets into the shredding mechanisms. The system works particularly well with substrate-free designs so that such designs have become preferred. However, the inventors have now realized another unanticipated problem with such designs.
In a substrate-free lubrication package, the liquid oil may redistribute within the sealed package in response to gravity. If the sheets are stored flat with their surfaces more or less parallel to the surface of the Earth, there is no problem. However, if the sheets are stored with their surfaces perpendicular to the surface of the Earth, the oil may pool at the lower edge of the package. Depending on the storage orientation of the packages, this can result in regions of the shredder blades not receiving sufficient lubricant. For example, if the oil is pooled along the left-hand edge of the lubrication sheet, the shredder blades towards the right-hand edge of the mechanism will not be properly lubricated.